【作者】 时晓梅；

【导师】 宾月珍； 松生胜；

【作者基本信息】 大连理工大学 ， 高分子材料， 2013， 博士

【摘要】 超高分子量聚乙烯(UHMWPE)因为具有良好的耐磨性、机械性能、抗腐蚀性以及生物相容性,而被广泛应用于人工关节材料。但是目前全人工关节置换术的长期追踪研究表明,关节置换术后假体的磨损是影响其使用寿命的主要因素。UHMWPE磨损颗粒引起的局部界面骨溶解,导致假体无菌松动,是造成人工关节置换失败的主要原因。所以,改善UHMWPE人工关节材料的抗磨损性能是至关重要的。本文通过用十氢萘和石蜡油作溶剂制备了UHMWPE溶液,通过凝胶化温度测试、小角激光光散射(SALS)、广角X-射线衍射(WAXD),考察了其凝胶化机理。结果表明石蜡油作溶剂时,由于其分子结构与UHMWPE分子链结构类似,有很好的亲和力,可能起到了交联点作用。UHMWPE分子链在106～108℃发生凝胶化,凝胶化与相分离关系不大。UHMWPE溶液的旋节线分离温度为109℃,远高于十氢萘作溶剂的88℃。而十氢萘作溶剂制备的UHMWPE溶液,是通过相分离形成聚合物富集区,导致凝胶化,从而促进了其凝胶结晶的过程。通过正交极化SALS和偏光显微镜(POM)对两种溶剂制备的UHMWPE溶液进行了观察,发现十氢萘作溶剂制备的UHMWPE溶液,在65-75℃淬冷,相分离的初期无散射图形,随着时间延长可以得到清晰的X形散射图形,相应的POM图片出现连续的网络结构。而石蜡油作溶剂制备的UHMWPE溶液,即使在室温下淬冷也只能得到模糊的圆形散射图形,相应的POM图片只显示出不是很清晰的连续结构。小角X-射线散射(SAXS)结果表明,两种溶剂制备的UHMWPE溶液的凝胶结晶机理不同,但得到干凝胶膜中的片晶结构基本相同,拉伸储能模量分别达到195和180GPa。以十氢萘和石蜡油作溶剂,通过溶液法制备了UHMWPE/羟基磷灰石(HA)复合溶液,用流变仪测试了复合溶液的粘度,并考察了其凝胶化时间。发现十氢萘的UHMWPE/HA复合溶液的粘度随着HA含量的增加,逐渐减小：而石蜡油作溶剂,则反之。十氢萘作溶剂制备UHMWPE/HA复合溶液的凝胶化时间,随着HA含量的增加逐渐缩短,在83℃,HA含量增加到31.5vo1%时,纯的UHMWPE溶液的凝胶化时间由3250s缩短到2700s。相反,石蜡油作溶剂时,随着HA含量的增加,凝胶化时间逐渐延长。在83℃,HA含量增加到31.5vo1%时,纯的UHMWPE溶液的凝胶化时间由1200s延长到1980s。通过扫描电镜(SEM)观察发现石蜡油作溶剂时,HA在UHMWPE基体中分散的更均匀。利用溶液法制备了一种具有梯度结构的UHMWPE/HA复合材料。通过摩擦测试发现,145～153℃下热压制备的UHMWPE/HA梯度复合材料的表面具有很好的抗磨损性。SEM和WAXD结果表明UHMWPE的(110)面平行于膜的表面发生了取向。衰减全反射红外(ATR)结果证明了150℃热压的UHMWPE膜和UHMWPE/HA复合膜,表面层下1.4μm以内无HA,而180℃热压的表面层含有HA,导致150℃热压的表面层比180℃热压的表面层的结晶度高。利用SEM和X-射线能量色散谱(EDS)观察发现UHMWPE/HA复合物在150℃热压时,大部分UHMWPE在HA表面重结晶,而在180℃热压时,大部分UHMWPE从HA表面熔融滑脱,小部分在HA表面重结晶。复合拉伸模量,剪切模量和泊松比受压膜温度的影响不大。随着HA含量的增加,复合泊松比的实部逐渐减小。当HA含量超过23.5vol%时,v’变为负值,表明UHMWPE/HA复合材料中出现了海绵结构。所以,随着HA含量增加,在高负载下,表面摩擦系数减小。摩擦系数、磨损率和弯曲测试性能都表明溶液法制备的UHMWPE/HA复合材料的结果要优于熔融法制备的。一系列的实验结果都证明,利用溶液法同时控制热压成型温度制备的UHMWPE/HA梯度复合材料会是一种很好的髋臼替代材料。聚乙烯醇(PVA)水凝胶具有化学性能稳定、生物相容性好、易成型及与自然关节软骨相似的结构和生物摩擦学特性,但是PVA作为髋臼材料的强度不够高,且难固定。基于此,将PVA与UHMWPE结合制备一种既具有低摩擦系数又易固定的梯度髋臼材料。利用合成锂皂石(laponite)作为模板剂能提高HA在水溶液中的分散性。用NaCl作为致孔剂,通过溶液法制备的多孔UHMWPE/HA复合材料孔隙率可达50%以上,孔洞分布均匀,并且内部含具有生物活性的HA颗粒,有利于提高UHMWPE与填充的PVA之间的界面结合强度；模拟人体关节软骨梯度结构制备的LBL复合PVA填充UHMWPE/HA梯度人工关节复合材料,在负载1200N时,摩擦系数可达0.017左右,接近人体关节软骨的摩擦系数,有望得到实际推广应用。更多还原

【Abstract】 Ultrahigh molecular weight polyethylene (UHMWPE) has been used in orthopedics as a bearing material in artificial joints because of notable properties such as chemical inertness, lubricity, impact resistance, and abrasion resistance. However, wear damages of the UHMWPE have been one of the factors limiting implant longevity. That is, the resultant wear of polyethylene bearing purportedly produces billions of wear particles with submicrometer size that cause adverse pathological reaction in the surrounding tissues leading to osteolysis and joint loosening. Therefore, to improve the wear resistance of the UHMWPE material used for artificial joint is essential.UHMWPE solution was prepared by decalin and paraffin. Gelation mechanism was investigated by gelation time, small angle laser light scattering (SALS) and Wide-angle X-ray diffraction (WAXD). When paraffin as the solvent, paraffin maybe becomes the role of crosslinking point for the UHMWPE moleculars. So the gelation temperature (106～108℃) and spinodal temperature (109℃) of UHMWPE solution prepared by paraffin are much higher than prepared by decalian (83℃and88℃). HV SALS and Polarized microscope (POM) were used to observe the structure of the UHMWPE solution. When the UHMWPE solution prepared by decalin quenched at65～75℃, X-type pattern and continuous structure can be seen, but, for paraffin as the solvent, even at room temperature only circle-type pattern and very small continuous structure can be seen. The Small Angle X-ray Scattering (SAXS) from the both films, however, showed the similar profiles indicating assemblies of crystal lamellae assuring ultradrawing.UHMWPE/HA composite solution was prepared by decalin and paraffin. Viscosity and gelation time were tested, the results shows that the viscosity and gelation time increase with the content of HA when decalin as the solvent, but in paraffin is inverse. When the content of HA reached31.5vol%at83℃, gelation time of UHMWPE/HA solution prepared by decalin shorten from3250s to2700s. However when paraffin as the solvent, the galation time prolonged from1200s to1980s. Scanning electron microscope (SEM) was used to observe the morphology of UHMWPE/HA composite, which indicates HA can be dispersed more uniform when paraffin as the solvent compared with decalin.UHMWPE/Hydroxyapatite (HA) composites which were prepared by the solution method and molded in the narrow temperature range145-153℃. WAXD intensity from UHMWPE film revealed high preferential orientation of the (110) plane with the highest atom density of the PE crystal unit. Attenuated total reflection (ATR) spectra from pristine UHMWPE films and UHMWPE/HA composites revealed that the existing probability of HA agglomerates on the surface layer (at ca.1.4μm depth) of the specimen molded at150℃was much lower than that molded at180℃, and the crystallinity of the thin layer was slightly higher. Furthermore, SEM observation and Energy Dispersive Spectrometer (EDS) spectra revealed that most of the HA agglomerates were covered by UHMWPE in the composites molded at150℃, UHMWPE chains under gelation were crystallized on the surface of HA agglomerates, but the partially flowed off UHMWPE chains from the surface of UHMWPE/HA agglomerates by molding at180℃were not recrystallized on the surface of HA agglomerates. The complex tensile moduli E*, complex shear moduli G*, and complex Poison’s ratio v*were hardly affected by the molding temperatures,150or180℃. Poisson’s ratio for the individual UHMWPE/HA composite and the gradient composite provided that the value became smaller with increasing HA content and tended to be negative beyond23.5vol%HA content, indicating an increase in voids in the spongy-like texture of the composites. Because of the descent degree of a number of voids in sponge-like tissues, surface fraction was smaller with increasing HA contents under high normal load. Of course, the frictional coefficient, wear rate, and bending properties prepared by solution were much superior to those prepared by a kneading method. A series of results suggested that by controlling molding temperature it turned out that the gradient composite prepared by the solution method provides great merits as an acceptable cup of bearing material in an artificial joint.Poly (vinyl alcohol)(PVA) Hydrogels have chemical stability, good biocompatibility, and easy to mold, also with similar structure and tribological properties of biological to natural articular cartilage. However, PVA material has low strength when as the acetabular materials, and difficult to be fixed. Based on this, to prepare a kind of gradient material combining UHMWPE with PVA has low friction coefficient and easy to be fixed.Laponite as a template was used to improve the dispersibility of HA in water. NaCl as the porogen was adopoted to prepare porous UHMWPE/HA composite by the solution method. Its porosity larger than50%and has uniform pore distribution. HA was introduced to reinforce the interfacial bonding effect between the LBL film and the PVA filling porous UHMWPE/HA composite, which has very low friction coefficient (0.017) under1200N near to the friction coefficient of natural articular cartilage. So the results indicated this kind of gradient material has the prospects to be used in for acetabular prosthesis in the future.更多还原